Conductive Bump Reciprocation Testing for Wafer-Stage Reliability
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Solution Overview
Problem
Existing semiconductor testing methods fail to effectively assess the reliability of conductive bumps under environmental conditions, particularly in temperature cycle tests, leading to issues like peeling and damage to BEOL wirings.
Innovation Solution
A test apparatus and method using a gripper that clamps conductive bumps and reciprocates them horizontally and vertically to simulate stress, measuring the time of crack occurrence in upper wirings, thereby evaluating the semiconductor device's reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bump pull test or bump shear test is applied, then the quality of conductive bumps can be confirmed, but environmental reliability tests such as temperature cycle test cannot be performed
Solution Approach 1:
The test apparatus applies dynamic reciprocating motion to the conductive bump using a gripper, simulating thermal expansion and contraction forces during temperature cycle testing. The bump is reciprocated horizontally between holders, creating cyclic stress that mimics environmental reliability conditions without requiring actual temperature cycling.
Solution Approach 2:
The patent replaces the need for thermal environment simulation with a mechanical reciprocating test system. Instead of applying thermal stress through temperature cycling, the apparatus uses mechanical reciprocation of the conductive bump to induce equivalent stress on the BEOL wirings, achieving environmental reliability assessment through mechanical means.
2Reliability
If temperature cycle test is performed to assess environmental reliability, then reliable testing can be achieved, but the test cannot be applied due to inability to cause peelings by continuous force
Solution Approach 1:
The test apparatus employs periodic reciprocating motion of the conductive bump, moving it back and forth horizontally between two holders. This periodic mechanical action creates cyclic stress on the bonding pad and BEOL wirings, equivalent to the thermal cycling effect, enabling environmental reliability testing through repeated mechanical cycles rather than thermal cycles.
Solution Approach 2:
The patent changes the test parameter from thermal cycling to mechanical reciprocation. By transforming the stress application method from thermal expansion/contraction to mechanical back-and-forth motion, the system achieves the same reliability assessment goal while avoiding the implementation complexities of temperature cycle testing.
3Reliability
If conventional testing is performed only at package stage, then reliable results can be obtained, but cost and time consumption increase
Solution Approach 1:
The test apparatus enables preliminary reliability testing of conductive bumps and BEOL wirings at the wafer stage, before packaging. By performing the reciprocating test on bare wafers with conductive bumps, potential defects can be detected early in the manufacturing process, avoiding the need for subsequent package-stage testing and reducing overall test time and cost.
Solution Approach 2:
The patent extracts the reliability testing function from the package stage and applies it directly at the wafer stage. By separating the bump and wiring reliability assessment from the packaged device testing, the system enables earlier detection of manufacturing defects, improving productivity by eliminating redundant testing steps later in the process.
Data Source
AI summary
A method of testing a semiconductor device includes forming conductive bumps respectively on a plurality of bonding pads of the semiconductor device. The semiconductor device having the conductive bumps is supported on a substrate stage. A gripper having first and second holders spaced apart from each other is positioned over the conductive bump. The conductive bump is clamped between the first and second holders. The gripper clamping the conductive bump is reciprocated at a constant speed with a predetermined stroke in a horizontal direction parallel with an upper surface of the substrate stage. A reliability of the semiconductor device is determined by measuring a time point at which a crack occurs in an upper wiring connected to the bonding pad.